Griffin Mazeski finished 106th overall but finished second in his age group at the America’s Finest City Half Marathon in San Diego, finishing in 1 hour, 33 minutes, 45 seconds in the 1-17 division, according to the race website. Mazeski’s time broke the record for a 9-year-old racer, set in 2015 by Liam Ballard at St. Petersburg Beach, Florida. Ballard finished in 1:34:59, according to the Association of Road Racing Statisticians.

"It was pretty hard and I didn't know if I could really break the record because I didn't feel that prepared coming into it,” said Mazeski, who is from Aurora, Colorado. "The first 11 (miles),, I mean, I felt really good and I was going under my pace that I wanted and I felt really calm and I could breathe easily, but at mile 12 there was a really long hill and I sort of died out on that.”

Mazeski turned 10 on Aug. 23. He wanted to run the 13.1-mile race for his birthday, KUSA reported.

"I thought it would be a cool experience and I think that it would be a really big accomplishment," he said.